The UK government's science and technology policy over the past two decades has sought to exploit the scientific knowledge base to improve innovation and economic competitiveness, by promoting stronger collaboration between university and industry, and stimulating academic entrepreneurship (Lambert, 2003). This study investigates the generative mechanisms for science-industry knowledge transfer in the food sector, especially for Small and Medium Sized Enterprises (SMEs) in the UK. Some of the central mechanisms that cause the transfer of new scientific insights to SMEs are outlined including: non-pecuniary incentives, reputation, opportunity, instrumental rationality, self-interest, strategic calculation, aggregation, learning and adaptive self-regulation. Whilst there is evidence that scientists are increasingly engaging in commercial activities, what remains unknown is whether they are driven by the same for-profit mechanism as in the traditional private sector. This study looks into the different levels of analysis with a multi-framework that examines: (1) structure or situational mechanisms; (2) agency or action-formation mechanisms; and (3) interactions or transformational mechanisms. The main research questions are: (1) what are the key generative mechanisms within science-industry knowledge transfer? and (2) what are the implications of these mechanisms to policy-making? Consequently, the main objectives of this study are: (1) to reveal the generative mechanisms of science-industry knowledge transfer, that go beyond an economic view to include social norms; and (2) to contextualise the implications for policy-making, to improve science-industry collaboration, engagement and outcomes. This research applies explaining-outcome process-tracing by investigating different knowledge transfer projects, utilizing empirical data from 52 in-depth interviews with scientists and food SMEs. In addition, 17 supporting project documents were reviewed and analysed. Systematic combining was then used to develop a narrative from empirical data, where the evidence leads to the formation of the most plausible explanation, followed by the abstraction of mechanisms which are then matched to a suitable theoretical framework. The results from the study show a range of mechanisms that caused knowledge transfer. The overall conclusion is that for most cases, the construction of relationships based around social norms, autonomy and relatedness are more dominant in science-industry knowledge transfer relationships than a focus on financial incentives or transaction costs theories. [ABSTRACT FROM AUTHOR]